1. Technical Field
The present invention relates to oxygen absorber, oxygen absorbent resin composition, and oxygen absorbent film used preferably for foods, medicines, pharmaceuticals, cosmetics, electronic parts, and so on.
2. Background Art
Oxygen absorbers are contained in packages for foods, medicines, pharmaceuticals, cosmetics, electronic parts, and so on. Oxygen absorbers containing iron powder or an organic compound as a reactant are known. Of those, the ones containing iron powder as reactant are used widely in view of cost and oxygen absorption capability. However, it has been pointed out that the oxygen absorbers containing iron powder as a reactant have the following disadvantages: (1) being detected by a metal detector using in packaging line of foods, medicines, pharmaceuticals, cosmetics, electronic parts, and so on to examine a foreign body, and (2) a package containing the oxygen absorbers should not be heated in a microwave oven because ignition may result.
For oxygen absorbers containing an organic chemical as a reactant, those using ascorbic acid and gallic acid are known.
The oxygen absorber containing ascorbic acid as a reactant, which absorbs oxygen relying on the oxidation of ascorbic acid, is low in oxygen absorption capability and slow in absorption speed compared with those containing iron powder as a reactant. To increase the oxygen absorption speed of ascorbic acid, a composition containing gallic acid and metallic salt compounds, with a porphyrin metal complex added as a catalyst, was suggested (JP1996-57307A).
Meanwhile, the oxygen absorber using gallic acid as a reactant also requires an alkaline compound and water as its ingredients because it relies on the mechanism in which the hydrogen of the hydroxyl group and the carboxyl group of the gallic acid are dissociated under the existence of the alkaline compound and water, and then the dissociated hydrogen reacts with oxygen (JP1996-24639A and JP1998-15385A). Since the oxygen absorber using gallic acid as a reactant requires water as its ingredient as described above, it is not suitable for use in dried foods, medicines, pharmaceuticals, cosmetics, and electronic parts.